The invention concern a separation apparatus for a drying plant wherein the material to be dried is heated by the heat of condensation of a readily volatile fluid (e.g., kerosene) and where in the course of the heating process this fluid becomes mixed with a less volatile fluid. The separation apparatus is a part of a drying plant comprising an autoclave that is capable of being evacuated, a main evaporator, a steam condenser, control devices, measuring instruments, and storage tanks which are interconnected by means of a pipeline system.
Arrangements of this type are useful, for example, for treating transformers which must be dried and degasified before they are filled with oil. The insulation of transformers which are pre-impregnated or are being repaired contain oil. Then during the drying process this oil will be extracted from the insulation. It is well known that oil is soluble in various carbon derivatives (e.g., kerosene).
If the drop in steam pressure due to the raising oil concentration becomes excessive, it becomes necessary to separate the oil to avoid impairment of the heating-up process. To achieve this, processes are known wherein a partial flow of the liquid kerosene/oil mixture is conducted in to an evaporator from which the therein evaporated kerosene is fed to a condenser operated at a low pressure. This arrangement has the disadvantage that the thermal energy used for the separation process is lost.
Condensation-heating plants have been also proposed where not only a partial flow but all of the kerosene to be vaporized, together with the oil dissolved therein, is conducted to an evaporatior of sufficiently large respectively high capacity and temperature, wherein the thermal energy is not lost. See, for example, the film evaporator described in published German patent application No. 25 52 746. This process has the disadvantage, however, that so high temperatures are required to provide a low residue of kerosene in the separated oil, that certain degradation of the separated oil is inavoidable. This separation device has the further disadvantage of requiring large dimensions since it must generate the full vapor volume.